Controlled copper leach recovery circuit

ABSTRACT

The present invention relates generally to a process for controlled leaching and sequential recovery of two or more metals from metal-bearing materials. In one exemplary embodiment, recovery of metals from a leached metal-bearing material is controlled and improved by providing a high grade pregnant leach solution (“HGPLS”) and a low grade pregnant leach solution (“LGPLS”) to a single solution extraction plant comprising at least two solution extractor units, at least two stripping units, and, optionally, at least one wash stage.

FIELD OF INVENTION

The present invention relates generally to a process for controlledleaching and sequential recovery of two or more metals frommetal-bearing materials. In one exemplary embodiment, recovery of metalsfrom a leached metal-bearing material is controlled and improved byproviding a high grade pregnant leach solution (“HGPLS”) and a low gradepregnant leach solution (“LGPLS”) to a single solution extraction plantcomprising at least two solution extractor units, at least two strippingunits, and, optionally, at least one wash stage.

BACKGROUND OF THE INVENTION

Hydrometallurgical treatment of metal-bearing materials, such as metalores, metal-bearing concentrates, and other metal-bearing substances,has been well established for many years. Moreover, leaching ofmetal-bearing materials is a fundamental process utilized to extractmetals from metal-bearing materials. In general, the first step in thisprocess is contacting the metal-bearing material with an aqueoussolution containing a leaching agent or agents which extracts the metalor metals from the metal-bearing material into solution. For example, incopper leaching operations, especially copper from copper minerals, suchas chalcopyrite, chalcocite, covellite, malachite, pseudomalachite,azurite, chrysocolla, and cuprite, sulfuric acid in an aqueous solutionis contacted with copper-bearing ore. During the leaching process, acidin the leach solution may be consumed and various soluble components aredissolved thereby increasing the metal content of the aqueous solution.Other ions, such as iron may participate in the leaching of variousminerals as these ions participate in dissolution reactions.

The aqueous leach solution containing the leached metal can then betreated via a known process referred to as solution extraction whereinthe aqueous leach solution is contacted with an organic solutioncomprising a metal-specific extraction reagent, for example, an aldoximeand/or ketoxime or a mixture thereof. The metal-specific extractionreagent extracts the metal from the aqueous phase into the organicphase. Moreover, during the solution extraction process for copper andcertain other metals, a leaching agent may be regenerated in the aqueousphase. In the case where sulfuric acid is the leaching agent, sulfuricacid is regenerated in the aqueous phase when copper is extracted intothe organic phase by the extraction reagent. Iron ions, which should notbe extracted by the metal-specific extraction reagent, should berecycled to the leaching step to the maximum extent possible.

In a standard agitation leaching process for copper, followed bysolution extraction, the leach solution is diluted to a lesser orgreater extent with acidified water in conjunction with the solid-liquidseparation process needed to provide a clarified leach liquor and soliddischarge. The diluted clarified leach solution then undergoes solutionextraction wherein copper is removed from, and the sulfuric acidconcentration is increased in, the aqueous phase. A portion of thiscopper-depleted, acid-containing aqueous phase, now called theraffinate, may be recycled back to the leaching process, recycled to thefront of the solid-liquid separation process, and/or forwarded tosecondary metal extraction processes, including but not limited tocobalt recovery.

However, under these current leaching and solution extraction processes,large concentrations of soluble metal and metal precipitate can be lostin the metal-depleted, acid-containing aqueous phase raffinatesolutions. These losses lead to inefficiencies and low overall processyields. Additionally, these high metal concentrations in the raffinatemake recovery of secondary metals costly and possibly impractical.

Accordingly, a process circuit for controlling the concentration ofmetal, especially copper, in the raffinate solution which is the feedfor the subsequent recovery of secondary metals without negativelyaffecting the primary metal recovery circuit would be advantageous.

SUMMARY OF THE INVENTION

The present invention relates generally to a process for controlledleaching and sequential recovery of two or more metals frommetal-bearing materials. In one exemplary embodiment, recovery of metalsfrom a leached metal-bearing material is controlled and improved byproviding a high grade pregnant leach solution (“HGPLS”) and a low gradepregnant leach solution (“LGPLS”) to a single solution extraction plantcomprising at least two solution extractor units, at least two strippingunits, and, optionally, at least one wash stage.

For example, in accordance with the various exemplary embodiments of thepresent invention, the present process comprises (a) providing a HGPLSto a solution extractor unit within a single solution extraction plant,(b) producing a high grade raffinate and a metal-loaded organic solutionby contacting the HGPLS with a partially loaded organic solution in thesolution extractor, (c) providing a LGPLS to a different solutionextractor unit within the same solution extraction plant, and (d)producing a low grade raffinate and the partially loaded organicsolution by contacting the LGPLS with a barren organic flow containing ametal-specific extraction reagent. Furthermore, in accordance with thevarious embodiments of the present invention, the flow rate and reagentconcentration of the barren organic flow containing a metal-specificextraction reagent can be altered based on the incoming metal materialquality to maintain a constant concentration of metal in the low graderaffinate, allowing for efficient secondary metal recovery, includingbut not limited to cobalt recovery. In accordance with an exemplaryembodiment of the present invention, the concentration of metal in theLGPLS may be adjusted by blending a portion of the LGPLS with the highgrade pregnant leach solution so that the quantity of metal entering thelow grade extraction circuit remains substantially constant.

BRIEF DESCRIPTION OF THE DRAWING

A more complete understanding of the present invention, however, maybest be obtained by referring to the detailed description whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements and wherein:

FIG. 1 illustrates a flow diagram of a general metal recovery process inaccordance with the present invention;

FIG. 2A illustrates a flow diagram of an alternate preparation processin accordance with the present invention;

FIG. 2B illustrates a flow diagram of an exemplary embodiment of a metalrecovery process in accordance with the present invention;

FIG. 3 illustrates a solution extraction process in accordance with thepresent invention; and

FIG. 4 illustrates one solution extraction plant for processing multipleleach solution streams in accordance with an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The detailed description of exemplary embodiments of the inventionherein shows various exemplary embodiments and the best modes, known tothe inventors at this time. These exemplary embodiments and modes aredescribed in sufficient detail to enable those skilled in the art topractice the invention and are not intended to limit the scope,applicability, or configuration of the invention in any way. Rather, thefollowing disclosure is intended to teach both the implementation of theexemplary embodiments and modes and any equivalent modes or embodimentsthat are known or obvious to those of reasonable skill in the art.Additionally, all included figures are non-limiting illustrations of theexemplary embodiments and modes, which similarly avail themselves to anyequivalent modes or embodiments that are known or obvious to those ofreasonable skill in the art.

Various embodiments of the present invention exhibit significantadvancements over prior art processes, particularly with regard to metalrecovery and process efficiency. Moreover, existing copper recoveryprocesses that utilize a reactive process for metal recovery/solutionextraction/electrowinning process sequence may, in many instances, beeasily retrofitted to exploit the many commercial benefits the presentinvention provides.

Referring to FIG. 1, in accordance with various aspects of the presentinvention, a metal-bearing material 100 is provided for processing.Metal-bearing material 100 may be an ore, a concentrate, or any othermaterial from which copper and/or other metal values may be recovered.Metal values such as, for example, copper, gold, silver, zinc, platinumgroup metals, nickel, cobalt, molybdenum, rhenium, uranium, rare earthmetals, and the like, may be recovered from metal-bearing materials inaccordance with various embodiments of the present invention. Thevarious aspects and embodiments of the present invention, however, proveespecially advantageous in connection with the recovery of copper fromcopper-bearing materials, such as, for example, ores and/or concentratescontaining chalcopyrite (CuFeS₂), chalcocite (Cu₂S), bornite (Cu₅FeS₄),and covellite (CuS), malachite (Cu₂CO₃(OH)₂), pseudomalachite(Cu₅[(OH)₂PO₄]₂), azurite (Cu₃(CO₃)₂(OH)₂), chrysocolla((Cu,Al)₂H₂Si₂O₅(OH)₄.nH₂0), cuprite (Cu₂O), brochanite(CuSO₄.3Cu(OH)₂), atacamite (Cu₂[OH₃Cl]) and other copper-bearingminerals or materials and mixtures thereof. Thus, metal-bearing material100 preferably is a copper ore or concentrate containing at least oneother metal value.

Metal-bearing material 100 may be prepared in preparation step 201 formetal recovery processing in any manner that enables the conditions ofmetal-bearing material 100—such as, for example, composition andcomponent concentration—to be suitable for the chosen reactiveprocessing method, as such conditions may affect the overalleffectiveness and efficiency of metal recovery operations. Desiredcomposition and component concentration parameters can be achievedthrough a variety of chemical and/or physical processing stages, thechoice of which will depend upon the operating parameters of the chosenprocessing scheme, equipment cost and material specifications. Forexample, as discussed in some detail herein below, metal-bearingmaterial 100 may undergo combination, flotation, blending, and/or slurryformation, as well as chemical and/or physical conditioning inpreparation step 201 before metal extraction.

Referring again to FIG. 1, in an exemplary embodiment of the presentinvention, after metal-bearing material 100 has been suitably preparedin preparation step 201 for metal recovery processing, it may beforwarded to a reactive processing step 202, for example, metalextraction. The reactive processing step 202 may be any suitable processor reaction that puts a metal in the metal-bearing material 100 in acondition such that it may be subjected to later metal recoveryprocessing. For example, exemplary suitable processes include reactiveprocesses that tend to liberate the desired metal value or values in themetal bearing material 100 from the metal-bearing material 100. Inaccordance with a preferred embodiment of the present invention, asdescribed in greater detail below, reactive processing step 202 maycomprise a leaching process.

In one aspect of an exemplary embodiment of the present invention,conditioning of a metal-bearing solution after reactive process step 202begins by adjusting certain physical parameters in conditioning step203. For example, as discussed in some detail herein below, afterreactive processing 202 metal-bearing material 100 may undergo reagentadditions, flashing processes, one or more solid-liquid phase separationsteps including use of filtration systems, counter-current decantation(CCD) circuits, thickeners, clarifiers, or any other suitable device forsolid-liquid separation, in conditioning step 203 to prepare the metalsolubilized therein for recovery.

Further, referring again to FIG. 1, in an exemplary embodiment of thepresent invention, after metal-bearing material 100 has been suitablyconditioned in conditioning step(s) 203 it may be forwarded to solutionextraction step 204. In accordance with further aspects of thisexemplary embodiment, the conditioning step(s) 203 produces a high gradepregnant leach solution (“HGPLS”) 104, comprising high concentrations ofdissolved metal values, and a low grade pregnant leach solution(“LGPLS”) 105, comprising a lower concentration of dissolved metalvalues than found in the HGPLS 104. In another exemplary embodiment, asdiscussed in some detail herein below, the HGPLS 104 and LGPLS 105 maybe produced by separate reactive processing steps and/or separateconditioning steps.

Regardless of the reactive step which produces the HGPLS 104 and LGPLS105, in an exemplary embodiment of the present invention, at least oneHGPLS 104 stream and at least one LGPLS 105 stream is forwarded tosolution extraction step 204. In accordance with an exemplary embodimentof the present invention, solution extraction step 204 comprises onlyone solution extraction plant. For example, in accordance with anexemplary embodiment of the present invention, solution extraction plant204 may comprise multiple interconnected solution extraction trainswithin a single solution extraction plant 204. Generally, in accordancewith the various embodiments of the present invention, the singlesolution extraction plant 204 is housed in one facility. It should beunderstood that this disclosure teaches, inter alia, efficient andcontrollable metal solution extraction from more than two separatepregnant leach solution (“PLS”) feed streams containing two or morerecoverable metal values in a single solution extraction plant and thatany number of PLS streams are contemplated herein.

In contrast, the prior art teaches only multiple plant solutionextraction for more than one PLS feed stream. It should be understoodthat any multiple plant solution extraction design requires roughlytwice the equipment and capital cost in reference to a single solutionextraction plant.

Moreover, in accordance with an exemplary embodiment of the presentinvention, single solution extraction plant 204 comprises at least twosolution extractor units, at least two stripping units, and, optionally,at least one wash stage, which are housed in the same facility. Itshould be understood that this disclosure teaches, inter alia, anynumber of solution extractor units, any number of stripping units, and,optionally, any number of wash stages for processing any number of PLSstreams are contemplated herein.

Generally, as will be described in greater detail below, in accordancewith an exemplary embodiment of the present invention, LGPLS 105 issubjected to a solution extractor unit, wherein a barren organic flowcontaining a metal-specific extraction reagent extracts at least onemetal value from the LGPLS 105 into the organic phase to form apartially loaded organic solution and a low grade raffinate 107.Additionally, in accordance with an exemplary embodiment of the presentinvention, HGPLS 104 is subjected to a different solution extractor unitwithin the same solution extraction plant 204, wherein the partiallyloaded organic solution further extracts at least one metal value fromthe HGPLS 104 into the organic phase to form a metal-loaded organicsolution, rich electrolyte, 106, preferably containing a highconcentration of primary metal values, and a high grade raffinate.

Further, referring again to FIG. 1, in an exemplary embodiment of thepresent invention, after solution extraction step 204, the resultingmetal-loaded solution 106 may be forwarded to primary metal recovery,illustrated as step 206. In accordance with various aspects of thepresent invention primary metal recovery step 206 may be any metalrecovery process, for example, electrowinning, sulphidation,precipitation, ion exchange or any other process suitable for recoveryof metals, may be utilized. In an exemplary embodiment of the presentinvention metals to be recovered in primary metal recovery step 206 mayinclude copper, silver, platinum group metals, molybdenum, zinc, nickel,cobalt, uranium, rhenium, rare earth metals, and the like. In apreferred exemplary embodiment of the present invention, primaryrecovery step preferably comprises an electrowinning circuit suitablydesigned to carry out any electrowinning process capable of producing ametal cathode product 208.

Similarly, referring again to FIG. 1, in an exemplary embodiment of thepresent invention, after solution extraction step 204, the resulting lowgrade raffinate 107 may be forwarded to one or more secondary metalrecovery steps 207. In an exemplary embodiment of the present invention,additional electrowinning circuits may be employed in the secondarymetal recovery step 207. Moreover, in an exemplary embodiment of thepresent invention, the secondary metal recovery step 207 may compriseany metal recovery process, for example, electrowinning, sulphidation,precipitation, ion exchange, cyanidation, or any other process suitablefor recovery of secondary metals. Preferably, as discussed in somedetail herein below, in an exemplary embodiment of the presentinvention, precipitation processes are used, thus making it advantageousto have low concentrations of primary metals in the low grade raffinate.Additionally, in an exemplary embodiment of the present invention,secondary metals to be recovered in secondary metal recovery step 207may include, silver, platinum group metals, molybdenum, zinc, nickel,cobalt, uranium, rhenium, rare earth metals, and the like.

Now with reference to FIG. 1 and FIG. 2B, in accordance with one aspectof the present invention, metal-bearing material 100 may optionally beprepared in a preparation step 201 comprising controlled grinding 200.More precisely, U.S. Pat. No. 6,676,909 describing controlled grindingis contemplated herein and the subject matter of that patent is herebyincorporated by reference. Preferably, a uniform particle sizedistribution is achieved. Additionally, process water 300 is preferablyadded to metal-bearing material stream 100 to bring the percent solidsto the optimal pulp density specified for the controlled grinding unit200. It should be understood that a variety of acceptable techniques anddevices for reducing the particle size of the copper-bearing materialare currently available, such as ball mills, tower mills, grindingmills, attrition mills, stirred mills, horizontal mills and the like,and additional techniques may later be developed that may achieve thedesired result of reducing the particle size of the copper-bearingmaterial to be transported.

Referring again to both FIG. 1 and FIG. 2B, in an exemplary embodimentof the present invention, after metal-bearing material 100 has beensuitably prepared for metal recovery processing, optionally bycontrolled grinding 200, and other physical and/or chemical conditioningprocesses, including but not limited to a thickening process, it may becombined with any number of liquid feed stream, represented by numericalreference 307, to form a metal-bearing inlet stream 101. Preferably, inan exemplary embodiment of the present invention, the liquid feed stream307 comprises process water, but any suitable liquid may be employed,such as, for example, recycled raffinate, pregnant leach solution, leanelectrolyte, and/or other recycled streams from the metal recoveryprocesses, including but not limited to secondary metal, such as cobaltor iron, recovery process streams.

Further, in an exemplary embodiment of the present invention,metal-bearing inlet stream 101 is subjected to a reactive processingstep 202 (FIG. 1), for example, metal extraction. The reactiveprocessing step 202 (FIG. 1) may be any suitable process or reactionthat puts a metal in metal-bearing material 100 in a condition such thatit may be subjected to later metal recovery processing. In accordancewith one embodiment of the present invention, reactive processing step202 (FIG. 1) comprises a leaching step 201 (FIG. 2B). Furthermore, in anexemplary embodiment of the present invention, the leaching process maycomprise any leaching process suitable for extracting the metal inmetal-bearing material 100 into an aqueous leach solution 102. Inaccordance with one aspect of the present invention, the leach step 201comprises atmospheric leaching, pressure leaching, whole ore leaching,agitation leaching, heap leaching, stockpile leaching, pad leaching,thin-layer leaching and/or vat leaching, at either ambient or elevatedtemperatures. Preferably, pressure leaching 201 is a pressure leachingprocess operating at a temperature in the range of about 140° C. toabout 250° C. and more preferably in the range of about 150° C. to about220° C.

In accordance with an aspect of the present invention, the optimumtemperature range selected for operation will tend to maximize theextraction of copper and other metals, minimize acid consumption, andthereby minimize make-up acid requirements. That is, at highertemperatures, sulfide sulfur generally is converted to sulfate accordingto the following reaction:

4CuFeS₂+17O₂+4H₂O→2Fe₂O₃+4Cu²⁺+8H⁺+8SO₄ ²⁻  (1)

At lower temperatures, acid is generally consumed and elemental sulfuris formed according to the following reaction:

4CuFeS₂+8H⁺+5O₂→2Fe₂O₃+4Cu²⁺+8S°+4H₂O  (2)

Thus, in accordance with one aspect of the present invention, in orderto maintain preferable leaching temperature, a cooling liquid 301 may beintroduced into the leaching vessel 201 during leaching. In accordancewith one aspect of this embodiment of the present invention, a coolingliquid 301 is preferably contacted with the feed stream in leachingvessel 201 during leaching. Cooling liquid 301 may comprise make-upwater, but can be any suitable cooling fluid from within the process orfrom an outside source, such as recycled liquid phase from the productslurry or a mixture of cooling fluids. Cooling liquid may be introducedinto leaching vessel 201 through the same inlet as metal-bearing inletstream 101, or in any manner that effectuates cooling of metal-bearinginlet stream 101. The amount of cooling liquid added during leaching mayvary according to the pulp density of the metal-bearing inlet stream101, as well as other parameters of the leaching process. In anexemplary aspect of this embodiment of the invention, a sufficientamount of cooling liquid 301 is added to leaching vessel 201 to yield asolids content in product slurry 102 on the order of less than about 50%solids by weight, more preferably ranging from about 3 to about 35%solids by weight, and most preferably ranging from about 10% to about20% solids by weight.

Moreover, in accordance with one aspect of the present invention,leaching step 201 may occur in any pressure leaching vessel suitablydesigned to contain the pressure leaching mixture at the desiredtemperature and pressure conditions for the requisite pressure leachingresidence time. In accordance with one aspect of an exemplary embodimentof the invention, the pressure leaching vessel used in leaching step 201is an agitated, multi-compartment pressure leaching vessel. However, itshould be appreciated that any pressure leaching vessel that suitablypermits metal-bearing material 100 to be prepared for metal recovery maybe utilized within the scope of the present invention.

During leaching step 201, copper and/or other metal values may besolubilized or otherwise liberated in preparation for later recoveryprocesses. Any substance that assists in solubilizing the metal value,and thus releasing the metal value from a metal-bearing material, may beused. For example, where copper is the metal being recovered, an acid,such as sulfuric acid, may be contacted with the copper-bearing materialsuch that the copper may be solubilized for later recovery steps.However, it should be appreciated that any suitable method ofsolubilizing metal values in preparation for later metal recovery stepsmay be utilized within the scope of this invention.

In accordance with one aspect of the present invention, during pressureleaching in leaching vessel 201, sufficient oxygen 302 is injected intothe vessel to maintain an oxygen partial pressure from about 50 to about200 psi, preferably from about 75 to about 750 psi and most preferablyfrom about 100 to about 400 psi Furthermore, due to the nature of mediumtemperature pressure leaching, the total operating pressure in leachingvessel 201 is generally superatmospheric.

The residence time for the pressure leaching process can vary, dependingon factors such as, for example, the characteristics of thecopper-bearing material and the operating pressure and temperature ofthe pressure leaching vessel. In one aspect of an exemplary embodimentof the invention, the residence time for the pressure leaching rangesfrom about 30 to about 180 minutes, more preferably from about 60 toabout 120 minutes.

Subsequent to metal-bearing material 100 undergoing leaching step 201,the metal values that have been made available by the leaching processundergo one or more of various conditioning steps 203 (FIG. 1). In oneexemplary embodiment, the product stream 102 from leaching step 201 maybe conditioned to adjust the composition, component concentrations,solids content, volume, temperature, pressure, and/or other physicaland/or chemical parameters to desired values and thus to form a suitablemetal-bearing solution. Generally, a properly conditioned metal-bearingsolution will contain a relatively high concentration of soluble metal,for example, copper sulfate, in an acid solution and preferably willcontain few impurities. Moreover, the conditions of the metal-bearingsolution preferably are kept substantially constant to enhance thequality and uniformity of the copper product ultimately recovered.

In one aspect of an exemplary embodiment of the present invention,conditioning of a metal-bearing solution for metal recovery begins byadjusting certain physical parameters of the product slurry 102 from theleaching step 201. Optionally, in an exemplary aspect of this embodimentof the invention, wherein the leaching step 201 is pressure leaching, itis desirable to reduce the temperature and pressure of the productslurry, in some instances to approximately ambient conditions. Anexemplary method of so adjusting the temperature and pressurecharacteristics of the product slurry is flashing 202 (FIG. 2B). In oneaspect of an exemplary embodiment of the present invention, flashingstep 202 (FIG. 2B) comprises atmospheric flashing. Further, flashedgases, solids, solutions, and steam may optionally be suitably treated,for example, by use of a Venturi scrubber wherein water may be recoveredand hazardous materials may be prevented from entering the environment.

In accordance with further aspects of this exemplary embodiment, eitherthe slurry product 102 directly from the leach process 201 or theflashed product slurry 103, if subjected to a flashing step 202 (FIG.2B), may be further conditioned in preparation for later metal-valuerecovery steps. For example, one or more solid-liquid phase separationsteps 203 (FIG. 2B) may be used to separate solubilized metal solutionfrom solid particles. This may be accomplished in any conventionalmanner, including use of filtration systems, counter-current decantation(CCD) circuits, thickeners, clarifiers, and the like. A variety offactors, such as the process material balance, environmentalregulations, residue composition, economic considerations, and the like,may affect the decision whether to employ a CCD circuit, a thickener, afilter, a clarifier, or any other suitable device in a solid-liquidseparation apparatus. In one aspect of an exemplary embodiment of theinvention, one or more solid-liquid phase separation steps 203 (FIG. 2B)may be carried out with a conventional CCD utilizing conventionalcountercurrent washing of the residue stream to recover leached metalvalues to one or more solution products and to minimize the amount ofsoluble metal values advancing with the solid residue to further metalrecovery processes or storage.

In accordance with further aspects of this exemplary embodiment, asexemplified in FIG. 2B, the solid-liquid phase separation step 203produces a high grade pregnant leach solution (“HGPLS”) 104, comprisinghigh concentrations of dissolved metal values, and a low grade pregnantleach solution (“LGPLS”) 105, comprising a lower concentration ofdissolved metal values than found in the HGPLS 104. Preferably, inaccordance with further aspects of this exemplary embodiment, large washratios are utilized in the solid-liquid phase separation steps 203—thatis, relatively large amounts of wash water are added to either theslurry product 102 or, if after the product slurry has been subjected toa flashing step 202, the flashed product slurry 103. This wash watercollects the remaining dissolved metal values and thus becomes the LGPLS105.

As further discussed herein below, the separated solids may further besubjected to later processing steps, including other metal recovery,such as, for example, recovery of gold, silver, platinum group metals,molybdenum, zinc, nickel, cobalt, uranium, rhenium, rare earth metals,and the like, by sulphidation, cyanidation, or other techniques.Alternatively, the separated solids may be subject to impoundment ordisposal.

The liquid separated from a solid-liquid phase separation step 203 mayalso undergo a series of conditioning steps to prepare the metalsolubilized therein for recovery. For example, the separated liquid mayundergo various reagent additions to put the metal in a state such thatthe metal is susceptible to conventional metal recovery techniques.Further, subsequent conditioning and/or processing steps may beundertaken such that recovery rates are as efficient as possible.

Referring to FIG. 1 and FIG. 2B, in accordance with an exemplaryembodiment of the present invention, after any desired conditioningsteps 203 (FIG. 1), for example, addition of diluting solution 303, theHGPLS 104 and LGPLS 105 may be forwarded to the desired metal recoverystep. The copper recovery step may include any suitable conditioningand/or copper recovery method or methods, for example, electrowinning,precipitation, solution extraction (sometimes referred to as solventextraction or liquid ion exchange), ion exchange, and/or ion flotation,and preferably results in a relatively pure copper product.Additionally, in accordance with an exemplary embodiment of the presentinvention, diluting solution 303 may be any suitable liquid, forexample, water or atmospheric leach effluent solution, that sufficientlyreduces the copper and acid concentrations to desired levels to providedesirable equilibrium conditions for solution extraction 204. Inaccordance with an exemplary embodiment of the present invention,sufficient amount of diluting solution 303 is added to yield an acidconcentration ranging from about 2 to about 25 grams/liter, and morepreferably from about 4 to about 7 grams/liter and a pH preferablyranging from about pH 1.5 to about pH 2.5 and more preferably from aboutpH 1.8 to about pH 2.2, and optimally in the range of about pH 2.0. TheHGPLS 104 and LGPLS 105 may thereafter be processed, such as for examplein accordance with metal extraction by solution extraction 204.

In many instances, due to variation in incoming metal tenor in themetal-bearing material 100, it is advantageous to mix one or more leachsolutions prior to solution extraction. As discussed briefly above, itis sometimes necessary to process two or more separate leach solutionstreams from multiple leach processes at one time. For example, if anoperation has both a heap leach operation and a pressure or agitatedleach operation, then the heap leach solution, equivalent to the LGPLS105, may need to be processed with a more concentrated pregnant leachsolution, HGPLS 104. In this instance, with reference to FIG. 2A andFIG. 2B and in accordance with an exemplary embodiment of the presentinvention, it is not required that the HGPLS 104 and LGPLS 105 areproduced from the same leaching step 201, flashing step 202, and/orsolid-liquid phase separation step 203. Stated another way, withreference to FIG. 2A and FIG. 2B and in accordance with an exemplaryembodiment of the present invention, either the HGPLS 104 or the LGPLS105 can be produced by one or more reactive processing steps 202.Additionally, with reference to FIG. 2A and FIG. 2B and in accordancewith an exemplary embodiment of the present invention, multiplecontrolled grinding steps 200, flashing steps 202, and/or solid-liquidphase separation steps 203 can be utilized to produce either the HGPLS104 or the LGPLS 105.

As mentioned above, the metal tenor in the metal-bearing material 100can vary greatly over the course of operating a metal recovery plant.Due to this variation, both primary and secondary metal recoveryprocesses can evidence losses in efficiency and overall processingyields. One reason for these losses is the inability to control and tunethe metal tenor in the raffinate from solution extraction of the LGPLSextraction, low grade raffinate. For example, low grade raffinate ispreferably subjected to a selective precipitation process wherein allmetal ions except for those of the secondary metal to be recovered, forexample cobalt, are eliminated from the process stream by precipitatingthem as solids. The precipitated primary metal solids may be recycled tothe reactive step. These precipitated solids may have a high probabilityof being rendered unrecoverable depending on the precipitating mechanismemployed. In the instance where there is high primary metal tenor in thelow grade raffinate, the amount of precipitated primary metal solidsrecycled to the reactive step may increase. This increase inprecipitated metal solids may lead to process inefficiencies due to highcirculating loads in process steps 202 and 204 (FIG. 2B).

Similarly, the inability to control and tune the metal tenor in the lowgrade raffinate directly affects the costs associated with the secondarymetal recovery processes. For instance, low metal tenors in the lowgrade raffinate require less reagent to effect precipitation (operatingcost savings), thus smaller equipment can be used to recycle the copperprecipitate (capital cost savings).

The present metal recovery process with single extraction plantadvantageously allows for control and tuning of the low grade raffinate.Moreover, the solution extraction process 204, described in detailbelow, preferably, allows for control and tuning of the low graderaffinate by adjustment of the barren organic flow rate and/oradjustment of the reagent content and/or adjustment of the flow of thefeed material and/or adjusting the metal content by blending ordilution, and/or any combinations thereof. It should be understood thatany of these parameters or others may be advantageously adjusted orcontrolled as may be desired to suitably adjust the copper flux to thereactive process. Additionally, in accordance with an exemplaryembodiment, the overall efficiency of the reactive process may beinfluenced by blending the primary metal solids precipitated from thelow grade raffinate with high grade raffinate prior to recycling to thereactive process step.

By making any of these adjustments to control and tune the metal tenorin the low grade raffinate, the low grade raffinate should preferablycontain very limited amounts of the primary metal and allows forefficient secondary metal processing. Additionally, the metal recoveryprocess and solution extraction plant described below, allows plantoperators to maintain a substantially controlled metal concentration inboth the LGPLS stream and the low grade raffinate stream.

Generally, in accordance with exemplary embodiments of the presentinvention, the controllable process within solution extraction plant 204comprises (a) providing a HGPLS to a solution extractor unit within asingle solution extraction plant, (b) producing high grade raffinate anda metal-loaded organic solution by contacting the high grade leachsolution with a partially loaded organic solution in the solutionextractor, (c) providing a LGPLS to a different solution extractor unitwithin the same solution extraction plant, and (d) producing a low graderaffinate and the partially loaded organic solution by contacting theLGPLS with a barren organic flow containing a metal-specific extractionreagent.

As discussed above, in accordance with the various embodiments of thepresent invention, the flow rate and concentration of the barren organicflow containing a metal-specific extraction reagent can be altered basedon the incoming metal ore quality to maintain a constant concentrationof metal in the low grade raffinate, allowing for efficient secondaryprocessing of other metals, including but not limited to cobaltrecovery. Because both the HGPLS and LGPLS streams are treated in onefacility, the metal content of the LGPLS may be controlled and heldconstant by adjusting LGPLS rate according to grade, with the excessbeing blended with the HGPLS.

In this regard, solution extraction plant 204 of FIG. 2 is described ingreater detail in FIG. 3. In accordance with an exemplary embodiment ofthe present invention, with reference to FIG. 3, the HGPLS 104 isprovided to a high grade solution extractor unit 209 and the LGPLS 105is provided to a low grade solution extractor unit 211. In accordancewith this exemplary embodiment of the present invention, HGPLS 104 has agreater concentration of metal than the LGPLS 105. In accordance withthis exemplary embodiment of the present invention, the LGPLS 105 has aconcentration of metal greater than about 20% of the concentration ofmetal in the HGPLS 104. Preferably, in accordance with this exemplaryembodiment of the present invention, the LGPLS 105 has a concentrationof metal greater than about 40% of the concentration of metal in theHGPLS 104. Most preferably, in accordance with this exemplary embodimentof the present invention, the LGPLS 105 has a concentration of metalgreater than about 50% of the concentration of metal in the HGPLS 104.

As discussed briefly above, in accordance with exemplary embodiments ofthe present invention, the LGPLS 105 is contacted with a barren organicflow containing a metal-specific extraction reagent 401, for example, analdoxime and/or ketoxime. The barren organic flow containing ametal-specific extraction reagent 401 extracts at least one primarymetal value from the aqueous phase of the LGPLS 105 into the organicphase. In accordance with exemplary embodiments of the presentinvention, the metal-specific extraction reagent is supplied by externalfeed 305. More specifically, in accordance with another exemplaryembodiment of the present invention, the LGPLS 105 is contacted with thebarren organic flow 401 in low grade solution extractor unit 211. Itshould be understood that the solution extractor unit 211 is only anexemplary reference and may comprise multiple solution extractor units.

Further, in accordance with this exemplary embodiment of the presentinvention, upon extraction of the at least one primary metal value fromthe aqueous phase of the LGPLS 105, a low grade raffinate 107 and apartially loaded organic solution 400 are produced. In accordance withthis exemplary embodiment of the present invention, low grade raffinate107 is an aqueous stream containing at least one secondary metal valuesand containing very low primary metal tenor, thus the low graderaffinate is suitable for secondary metal recovery 207 as discussedabove with reference to FIG. 1 and further exemplified in FIG. 2B.

Secondly, in accordance with this exemplary embodiment of the presentinvention, the partially loaded organic solution 400 may be contactedwith the HGPLS 104 to produce a metal-loaded organic solution 402 and ahigh grade raffinate 304. Similarly, with reference to FIG. 3 and inaccordance with exemplary embodiments of the present invention, theHGPLS 104 is contacted with the partially loaded organic solution 400 inhigh grade solution extractor unit 209. As will be discussed in detailbelow, in accordance with exemplary embodiments of the presentinvention, metal-loaded organic solution 402 is forwarded to at leastone stripping unit 210 for recovery of at least one metal value. Itshould be understood that the solution extractor unit 209 is only anexemplary reference and may comprise multiple solution extractor units.

As discussed previously, it is desirable to produce a metal-loadedorganic solution 402 with high metal tenor, which is suitablyconditioned for metal recovery by stripping and electrowinning.Additionally, it is desirable to produce a low grade raffinate 107,which contains very low primary metal tenor and is suitable forsecondary metal extraction. In order to accomplish this, with referenceto FIG. 3 and in accordance with exemplary embodiments of the presentinvention, the barren organic flow rate may be varied in correlation tothe grade of the incoming metal-bearing material and may be produced inone or more stripping units 210. Additionally, in accordance withexemplary embodiments of the present invention, any metal-specificextraction reagent may be supplied by external feed 305 to the strippingunits 210 or any time prior to contacting the LGPLS 105. In accordancewith exemplary embodiments of the present invention, the concentrationof the metal-specific extraction reagent 305 may be varied incorrelation to the grade of the incoming metal-bearing material.

With reference to FIG. 3 and in accordance with exemplary embodiments ofthe present invention, the partially loaded organic solution 400 may besubjected to an optional stripping unit 210 prior to contacting theHGPLS 104. This intermediate optional stripping unit 210 may increasethe extraction effectiveness of the organic solution 400, therebyallowing for a lower reagent concentration without sacrificing metalextraction efficiency. It should be understood that this disclosureteaches, inter alia, any number of solution extractor units and anynumber of stripping units in any configuration.

As mentioned above, in accordance with exemplary embodiments of thepresent invention, the metal-loaded organic solution 402, preferablycontaining a high metal tenor, is subjected to stripping unit 210 and atleast one metal value is stripped from the metal-loaded organic solution402. In accordance with exemplary embodiments of the present invention,at least one metal value is stripped from the metal-loaded organicsolution 402 by using any fluid suitable for stripping metal values froma metal-loaded organic solution, preferably lean electrolyte 306recycled from an electrowinning circuit 216 (FIG. 2B). Optionally, inaccordance with exemplary embodiments of the present invention, themetal-loaded organic solution 402 is subjected to a wash stage 212 priorto being stripped in stripping unit 210.

High grade raffinate 304 from solution extraction plant 204 (FIG. 2B)may be used beneficially in a number of ways. For example, all or aportion of high grade raffinate 304 maybe recycled to any leaching step201 for temperature control or may be used in atmospheric leaching,pressure leaching, whole ore leaching, agitation leaching, heapleaching, stockpile leaching, pad leaching, thin-layer leaching, vatleaching, and/or may be used for a combination thereof at either ambientor elevated temperatures. The use of high grade raffinate 304 in heapleaching operations may be beneficial because the acid and ferric ironvalues contained in raffinate 304 can act to optimize the potential forleaching oxide and/or sulfide ores that commonly dominate agitationleaching, heap leaching, stockpile leaching, pad leaching, thin-layerleaching and/or vat leaching operations. That is, the ferric and acidconcentrations of raffinate 304 may be used to optimize the Eh and pH ofheap leaching operations. It should be appreciated that the propertiesof high grade raffinate 304, such as component concentrations, may beadjusted in accordance with the desired use of high grade raffinate 304.

Additionally, in accordance with the various embodiments of the presentinvention, low grade raffinate 107 from solution extraction plant 204(FIG. 2B) may be sent to secondary metal processing 207 (FIG. 1) forother secondary metals, including, but not limited to silver, platinumgroup metals, molybdenum, zinc, nickel, cobalt, uranium, rhenium, rareearth and actinide metals. As mentioned above, preferred embodiments ofthe present invention advantageously provide for maintenance of aconstant metal tenor in both the high grade and low grade raffinate.This direct control facilitates a known and substantially controlledmetal precipitate recycle, increasing operating efficiency, potentiallimiting metal losses, and reducing recycle equipment size andsubsequent capital costs. Therefore, in accordance with the variousembodiments of the present invention, the flow rate and concentration ofthe organic flow containing a metal-specific extraction reagent 401 canbe altered based on the incoming metal-bearing ore quality to maintain aconstant concentration (tenor) of metal in the low grade raffinate 107.To effectuate such direct control either the metal concentration and/orflow rate of any organic and/or aqueous flow in the process may becontrolled, thus enabling extraction to take place under tightlycontrolled conditions. Specifically, the amount of high grade raffinatewhich is recycled to a leach step may be controlled. This ability tomaintain the metal tenor of the low grade raffinate 107 allows for theefficient recovery of cobalt or other secondary metal values at anygiven metallic ore quality by removing a majority of primary metals,which would interfere with the recovery of other secondary metal, fromthe low grade raffinate 107.

With reference to FIG. 3, the present invention allows the extractioncircuit for the primary metal value to be tuned and optimized, both interms of metallurgical performance and capital and operating costs.There is a trade off between achieving optimum metallurgical performanceand minimizing the capital costs of the operating facility. Thedecisions made regarding this trade off are based on the performance andcost of the metal-specific extraction reagent employed as well as thechemistry of the pregnant leach solution streams to be treated. Forexample, the use of a metal-specific extraction reagent with exhibitsrapid extraction kinetics may minimize the number of sequentialextractors needed to achieve a satisfactory level of metal recovery. Thepresence of iron, manganese, or chloride in the pregnant leach solutionstreams may require the use of a wash stage prior to stripping. Thenumber and placement of stripping units is decided based on thestripping kinetics of the extraction reagent as well as its maximummetal loading capacity. Accordingly, various configurations are withinthe scope of the present invention.

Moreover, in accordance with this exemplary embodiment of the presentinvention, multiple solution extractor units can be utilized in anyconfiguration, preferably series or parallel configurations, within thesame solution extraction plant 204. More specifically, the high gradesolution extractor unit 209 is suitably connected in parallel to the lowgrade solution extractor unit 211 by a common organic flow containing ametal-specific extraction reagent. For example, in accordance with anexemplary embodiment of the present invention, as depicted in FIG. 4,low grade solution extractor unit 211 is separated from the high gradesolution series solution extractor unit 209 by at least one serialsolution extractor unit 213. Additionally, the low grade solutionextractor unit 211 is separated from the stripping unit 210 by at leaston serial solution extractor unit 204.

More precisely, with reference to FIG. 4 and the exemplary embodiment,the low grade solution extractor unit 211 and solution extractor unit214 are in a series configuration. Additionally, the high grade solutionextractor unit 209 and solution extractor unit 213 are in a seriesconfiguration. Moreover, it should be understood that it is not thenumber of solution extraction units employed, but the sequence in whichthey are configured, thus any number of solution extraction units can beemployed and are contemplated herein. Further, as illustrated by FIG. 3,the high grade extractor units may optionally be separated from the lowgrade extractor units by an intermediate strip unit 210 (FIG. 3), ifsolution chemistry and process kinetics make it advantageous to do so.Additionally, an organic wash stage 212 (FIG. 3) may be added prior tostripping if necessitated by solution chemistry.

Returning to FIG. 2B, in accordance with the various embodiments of thepresent invention, metal-bearing solution stream, or rich electrolyte,106 from solution extraction plant 204 may be sent to an electrolyterecycle tank 205. The electrolyte recycle tank may suitably facilitateprocess control for an electrowinning circuit 216, as will be discussedin greater detail below. Metal-bearing solution stream 106, which cancontain from about 25 to about 75 grams/liter of copper and from about145 to about 180 grams/liter acid, is preferably blended with a leanelectrolyte 306 (i.e., electrolyte that has already been through themetal recovery phase and has had a portion of its dissolved copperremoved) and makeup fluid 215, such as, for example, water, in theelectrolyte recycle tank 205 at a ratio suitable to yield a productstream 108, the conditions of which may be chosen to optimize theresultant product of electrowinning step 216.

In accordance with the various embodiments of the present invention, themetal composition of product stream 108 is maintained substantiallyconstant at a value from about 20 to about 60 grams/liter, morepreferably at a value from about 30 to about 50 grams/liter. Metalvalues from the product stream 108 are removed during electrowinningcircuit 216 to yield a pure, cathode metal product 217. As mentionedabove, in accordance with the various embodiments of the presentinvention, electrowinning circuit 216 produces pure, cathode metalproduct 217 and lean electrolyte 306, which can be recycled to theelectrolyte recycle tank 205, the solution extraction plant 204, and/orthe leaching step 201.

It should be appreciated that in accordance with the various aspects ofthe invention, a process wherein, upon proper conditioning of thecopper-bearing solution, a high quality, uniformly-plated cathode copperproduct may be realized without subjecting the copper-bearing solutionto solution extraction prior to entering the electrowinning circuit iswithin the scope of the present invention. As previously noted, carefulcontrol of the conditions of the copper-bearing solution entering anelectrowinning circuit—especially maintenance of a substantiallyconstant copper composition in the stream—can enhance the quality of theelectrowon copper by, among other things, enabling even plating ofcopper on the cathode and avoidance of surface porosity in the cathodecopper, which degrades the copper product and thus diminishes itseconomic value. In accordance with this aspect of the invention, suchprocess control can be accomplished using any of a variety of techniquesand equipment configurations, so long as the chosen system and/or methodmaintain a sufficiently constant feed stream to the electrowinningcircuit. As those skilled in the art are aware, a variety of methods andapparatus are available for the electrowinning of copper and other metalvalues, any of which may be suitable for use in accordance with thepresent invention, provided the requisite process parameters for thechosen method or apparatus are satisfied.

It is believed that the disclosure set forth above encompasses at leastone distinct invention with independent utility. While the invention hasbeen disclosed in the exemplary forms, the specific embodiments thereofas disclosed and illustrated herein are not to be considered in alimiting sense as numerous variations are possible. The subject matterof the inventions includes all novel and non-obvious combinations andsub combinations of the various elements, features, functions and/orproperties disclosed herein.

The method and system described herein may be implemented to recovercopper and other metals in a controlled manner. Other advantages andfeatures of the present systems and methods may be appreciated from thedisclosure herein and the implementation of the method and system.

1. A controlled copper leach and recovery process comprising: subjecting a metal-bearing material to a reactive process to liberate at least one metal value from said metal-bearing material; obtaining a product slurry from said reactive process, wherein at least two metal values are present in said product slurry; producing a high grade pregnant leach solution and a low grade pregnant leach solution by subjecting said product slurry to a solid-liquid separation process; providing said high grade pregnant leach solution to a solution extraction plant comprising at least two solution extractors and at least two stripping units; producing a high grade raffinate and a metal-loaded solution by contacting said high grade pregnant leach solution with a partially loaded organic solution in said solution extraction plant; providing said low grade pregnant leach solution to said solution extraction plant, wherein said low grade pregnant leach solution comprises a lower metal concentration than said high grade pregnant leach solution; and producing a low grade raffinate and said partially loaded organic solution by contacting said low grade pregnant leach solution with a barren organic flow for extracting said at least one metal value.
 2. The process of claim 1, wherein said reactive process comprises a leaching process.
 3. The process of claim 1, wherein at least one metal value is stripped from said metal-loaded solution in at least one stripping unit.
 4. The process of claim 3, wherein said barren organic flow is produced by stripping said at least one metal value in at least one stripping unit.
 5. The process of claim 4, wherein said partially loaded organic solution is subjected to at least one stripping unit prior to contacting said high grade pregnant leach solution.
 6. The process of claim 2, wherein said high grade raffinate is recycled to a leaching process.
 7. The process of claim 1, wherein the concentration of metal in low grade raffinate is held substantially constant by varying the flow rate of said barren organic flow or reagent concentration.
 8. The process of claim 1, wherein said low grade raffinate is subjected to secondary extraction processing.
 9. The process of claim 8, wherein the secondary metal to be extracted is at least one of gold, silver, platinum group metals, molybdenum, zinc, nickel, cobalt, uranium, rhenium, rare earth metals, and actinide metals.
 10. A controlled copper leach and recovery process comprising: providing a high grade pregnant leach solution to a first solution extractor unit; producing a high grade raffinate and a metal-loaded organic solution by contacting said first leach solution with a partially loaded organic solution; providing a low grade pregnant leach solution to a second solution extractor unit, wherein said high grade pregnant leach solution has a greater concentration of metal than said low grade pregnant leach solution and wherein said first solution extractor unit and said second solution extractor unit are in the same solution extraction plant; producing a low grade raffinate and said partially loaded organic solution by contacting said low grade pregnant leach solution with a barren organic flow; and producing said barren organic flow by stripping at least one metal value from said metal-loaded organic solution in at least one stripping unit within said solution extraction plant.
 11. The process of claim 10, further comprising adding a metal-specific extraction reagent to said barren organic flow prior to contacting with said low grade pregnant leach solution.
 12. The process of claim 10, wherein said high grade pregnant leach solution is generated from at least one of an atmospheric leaching process, a pressure leaching process, an agitation leaching process, a heap leaching process, a stockpile leaching process, a pad leaching process, a thin-layer leaching process, and a vat leaching process.
 13. The process of claim 10, wherein said high grade raffinate is recycled to at least one of a atmospheric leaching process, a pressure leaching process, an agitation leaching process, a heap leaching process, a stockpile leaching process, a pad leaching process, a thin-layer leaching process, and a vat leaching process.
 14. The process of claim 10, wherein said low grade raffinate is subjected to secondary extraction processing.
 15. The process of claim 14, wherein the secondary metal to be extracted is at least one of silver, platinum group metals, molybdenum, zinc, nickel, cobalt, uranium, rhenium, rare earth metals, and actinide metals.
 16. The process of claim 10, wherein said concentration of metal in said second leach solution is greater than about 20% of the concentration of metal in said first leach solution.
 17. The process of claim 10, wherein said first solution extraction unit is connected to said second solution extraction unit in parallel.
 18. The process of claim 10, wherein at least one stripping unit is positioned between said first solution extraction unit and said second solution extraction unit.
 19. The process of claim 10, wherein at least one solution extractor unit separates said first solution extraction from said second solution extractor unit.
 20. The process of claim 10, further comprising stripping said metal-loaded solution in at least one stripping unit to produce a metal-rich solution and a barren organic solution.
 21. The process of claim 20, further comprising sending said metal-rich solution to an electrowinning process.
 22. The process of claim 20, further comprising washing said metal-loaded solution in at least one wash stage prior to said stripping step.
 23. The process of claim 10, wherein the concentration of metal in low grade raffinate is held substantially constant by varying the flow rate of said barren organic flow.
 24. The process of claim 10, wherein the concentration of metal in said low grade raffinate is controlled by altering the flow rate of at least one of said high grade pregnant leach solution and said low grade pregnant leach solution.
 25. The process of claim 10, wherein said at least one metal value is stripped from metal-loaded solution by at least one of a lean electrolyte from an electrowinning process and a sulfuric acid solution. 